When making biochar for research purposes in a lab or workshop, using systems like muffle furnace or fixed bed pyrolyser or other pyrolyser systems, how do we know then when the biochar is ready and the feedstock has been converted to biochar completely? In other words, based on what indicators we decide the biochar is ready and we turn off the furnace?
Thank you so much for your answers.
Dear Dr Farhad Khorsandi ,
This is based on two major factors. One is the residence time selected by the experimenter and the other is the fuel properties of the biomass feedstock. Since residence time is an important parameter in pyrolysis, the research can set the time to say 30 mins, 45 mins, or 60 mins. At the expiration of the set time, the biochar can be retrieved.
However, it is important to state the reaction time also depends on the moisture (M) and volatile matter (VM) content of the feedstock. As a rule of thumb, the higher the M and VM, the longer the time required although the optimum time reported in literature for biomass pyrolysis is 60 mins. Hope this helps.
Best regards,
BBN
From my experiment using my design Gasification - Pyrolisis Stove, I found that we could also detect it using VM produce. when VM produce is going sharply decrease this is can be used as indicator of biochar is ready and we can harvest the biochar .
One day I think we can use sensor (VM) to detect this condition.
Best regard,
Johanis R. Pangala
Dear Dr. Nyakuma
Thank you so much for your time and well explanation of my question. So, maybe I should run some tests with different resident times to find the optimum time for my feedstock? I guess since different feedstocks have different chemical properties and VM, one should find the end time with trial and error before the actual experiment.
Best wishes and thank you again.
Dear Dr. Pangala
Thank you so much for your interesting answer and idea. When the muffle furnace is running, the VM comes out of the outlet under the ventilation hood. So in your opinion, when this VM smoke stoped, it would be a good indicator that biochar is ready?
best wishes
I agree with Johanis Pangala especially for high-temperature region (say > 700C). Hemicellulose and cellulose will have decomposed at < 400C. For lignin it is a bit more difficult to say because it is a heterogenous constituent and decomposes over a wide temperature range.
We use the Belonio rice husk gasifier at UniKL MICET, and when the gasification zone has reached the bottom of the updraft gasifier the smoke (if we don't burn it) stops. If we do not remove the char (fixed carbon) it will continue to burn until only ash is left.
Thank you so much Robert
very good and useful answer. I'm sure it will help me alot in our work.
Best wishes and thank you again.
Biochar is a byproduct of pyrolysis, the main products are bio-gas and bio-oil. That's why I am agree with Johanis Pangala. Sharp decrease of production of VM indicates that the main products (bio-gas nad bio-oil) are removed from the feed-stock and now the rest is biochar.
Thank you Dr. Sekhar Paul for sharing your opinion. I like Dr. Pangala's suggestion, and believe it is rational and practical. All the best.
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